The present invention relates to a fiber-reinforced rubber and more particularly to a reinforcement embedded in a rubber.
Since high plessley, high elasticity, high dimensional stability, and high adhesive strength has been required for rubbers such as a belt, a tire, and a hose, a reinforcing cord constructed by fibers or a reinforcing canvas is embedded in a rubber. Generally, cords consist of twisted yarns is used for the reinforcement. The cords is grouped into all-yarns-twisted cords, half-yarns-twisted cords, or lang lay. The all-yarns-twisted cords are most popular for reinforcement for a rubber.
However, when the all-yarns-twisted cords are embedded on a rubber as reinforcement, monofilaments rub each other at sharp angle within the all-yarns-twisted cord. Accordingly, the yarn is abraded, broken, or decreased in strength from that rubbed part after short period of usage. Therefore, flex fatigue is lowered.
Japanese Patent Application Laying Open Gazette No. 59-19744 proposed a fiber-reinforced rubber, which reinforcement is constructed by half-yarns-twisted cords or lang lay to solve the above problem (flex fatigue).
However, a rubber reinforced by half-yarns-twisted cords or lang lay is lowered in elongation and rate tensile elasticity after dipping process, comparing with a rubber reinforced by all-yarns-twisted cords. This results in lower dimensional stability.
Also, since the half-yarns-twisted cords or lang lay are twisted in only one direction, inversion and loose of cords are easily caused at all end. This makes the processing of the cord harder. Furthermore, fray is easily caused in a place where the cord is cut during processing of the cord.
When the half-yarns-twisted cords or lang lay are used as a reinforcement for the industrial belt, there exists a problem such that only one side of the belt is abraded soon since the running belt creeps to one side. This creep is caused by a twisted direction of the cords such like a half-yarns-twisted cord. On the other hand, the Japanese Patent Application Laying Open Gazette No. 56-103008 disclosed a conveyor belt, in which a reinforcement consists of half-yarns-twisted cords of S-twist and Z-twist alternately in order to prevent the uneven abrasion. However, in this case, two cords (both are half-yarns-twisted cords) arc set in parallel and spiral in a belt and accordingly, totally four places on right and left sides or the belt are cut in every pair of cords. Therefore, the maintainability of plessley is lowered.
On the other hand, a braided cord has been used for various purposes. Particularly, a tubular braid surpasses in flex fatigue due to its constructional properties, and it is also superior to a twisted cord in dimensional stability. Therefore, time tubular braid will improve both the flex fatigue and dimensional stability if it is used for a reinforcement for a rubber. Furthermore, in processing, the tubular braids possess an advantage such that loose, which occurs in half-yarns-twisted cords and lang lay at an end of cord by the inversion, is not caused. Therefore, cut end is not frayed at processing the tubular braids. Furthermore since tubular braids do not possess the twisted direction which half-yarns-twisted cords possess, time industrial belt maintains stable running without creeping and consequently, uneven abrasion can be prevented.
Although even the tubular braids possess various advantages as mentioned above, it need to be improved since some rubbers, where time tubular braids arc embedded for reinforcing, require higher bending fatigue and dimensional stability according to its usage and object.